In the manufacture of formed armature coils, wire wound field coils, solenoid coils, and other types of coils where a mechanically rigid self-supporting winding is desired it has been a normal processing procedure to apply a bushing or bakelizing resin between each of the layers of insulated conductor as it is being wound into the coil. The winding is then clamped or braced and is heated to cure the resin system. After curing, the clamps or braces are carefully removed and all excess cured resin residue and flashing are removed by grinding or other techniques.
This procedure is messy due to resin which drips off the coils. The wasted resin and the time required to brush on enamel also makes the procedure expensive. The final results vary due to the exactness and care of resin application. Also, workers can become sensitive to liquid resins which must be applied in open areas as this procedure requires.